Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

In the study, men who smoked, drank, used recreational drugs or had a high body mass index (BMI) were no more likely to have low sperm counts than those who did not engage in these behaviors. The researchers used low sperm counts as a measure of male fertility.

"This potentially overturns much of the current advice given to men about how they might improve their fertility and suggests that many common lifestyle risks may not be as important as we previously thought," said study researcher Dr. Andrew Povey, of the University of Manchester's School of Community Based Medicine.

Povey and colleagues gathered information from 2,249 men from 14 fertility clinics around the U.K., and asked them to fill out detailed questionnaires about their lifestyle. The information was then compared to 939 men with low sperm counts, and a control group of 1,310 men who produced higher numbers.

Men with low sperm counts were 2.5 times more likely to have had testicular surgery, twice as likely to be black, and 1.3 times more likely to do manual work and not wear boxer shorts.

Using recreational drugs, tobacco and alcohol, and having a high BMI were not associated with an increased risk of low sperm counts.

"In spite of our results, it's important that men continue to follow sensible health advice and watch their weight, stop smoking and drink alcohol within sensible limits," said study researcher Dr. Allan Pacey, of the University of Sheffield.

While the study did not find a link between smoking and low sperm count, it did not examine the effects of second hand smoke on the female partner's fertility, said Dr. Avner Hershlag, chief of the Center For Human Reproduction at North Shore University Hospital in Manhasset, N.Y., who was not involved in the study.

In addition, because the study was conducted in the U.K., the findings regarding black men may not apply to African-American men, Hershlag said.